Apparatus for removing excess coating material from strip edges

ABSTRACT

An edge wiper for removing excess coating material from a coated strip in a slow speed coating operation in which the coating weight control is effected by an air knife, includes means for vertical adjustment, a lever arm pivotally supported and associated with a counterweight to provide a biasing force, and means to transversely adjust the pivot support.

United States Patent Patterson [54] APPARATUSTFOR'REMOVING ExcEss COATING MATERIAL FROM STRIP EDGES [72] Inventor: Robert W. Patterson, Fairfield, Ala. [73] Assignee: United States Steel Corporation [22] Filed: Feb. 23, 1971 [21] Appl. No.: 117,987

[52] US. Cl ..118/63, 118/67 [51 1 Int. Cl ..B05c'. ll/06 [58] Field of Search ..118/63, 4, 8,121,122,115, 118/116,117,123,126,15/316-319, 207',

[56] References Cited UNITED STATES PATENTS Lasor ..1 18/ 1 22 Nieman et a1. ..1 18/ 103 n51- 3,685,484 1 Aug. 22, 1972 2,894,856 7/1959 Schwendemann et v.al ..118/63X 3,140,960 7/ 1964 Grabezyk et a1 ..1 18/122 3,149,988 9/1964 Penman ..118/123 X 3,375,805 4/1968 Beall et a1 188/63 3,499,418 3/1970 Mayhew ..1 18/63 X 3,536,038 10/1970 .LeCroy..... ..118/104 Primary Examiner-Morris Kaplan I Attorney-Ralph H. Dougherty 57 ABSTRACT An edge wiper for removing excess coating mnterinl from a coated strip in a slow speed coating operation in which the coating weight control is effected by an air knife, includes means for vertical adjustment, a lever arm pivotally supported and associated with a counterweight to provide a biasing force, and means to transversely adjust the pivot support.

1 Claim, 2 Drawing Figures PATENTEDAUBZZ I972 3.685.484

saw 1 or 2 FIG.

INVENTOR. ROBERT W. PATTERSON By T A r rorney PATENTEU M1922 3.685.484 SHEET 2 0F 2 INVENTOR. ROBERT KI. PATTERSON By Wm A r rarney APPARATUS FOR REMOVING EXCESS COATING 1 MATERIAL FROM STRIP EDGES This invention relates to an apparatus for removing excess coating material from the edges of coated stiip produced in a slow speed coating operation in conjunction with air knives which are used for coating weight control.

1 Air knives are used to control the weight and distribution of a coating applied in hot dip coating operations, such as the galvanizing of steel strip. Air or a fluid under pressure is directed against the face of a coated substrate as it emerges vertically from a bath of molten coating material. This acts as a squeegee, removing excess coating material and causing it to flow back down the strip into the bath. The air jets may be horizontal but are generally inclined downwardly from 5 to 45 from the horizontal with about 20 to 25' being preferred for slow speed lines. Air knives, such as shown in my US. Pat. No. 3,406,656, tend to avoid build-up of the coating metal at the edges of the substrate when the substrate travels at relatively high speeds. However, when hot dip coating lines, such as a minimum spangle galvanizing line, are operated at I speeds less than 150 feet per minute and air knives are used for coating control, whiskers are formed which adhere to each edge of the substrate. This is a particularly undesirable condition. Besides presenting a very unappealing appearance, whiskers cause safety and handling problems and can cause coiling difficulties. Further, the cost of production is increased by loss of coating material as whiskers.

It is the primary object of my invention to prevent the formation of dendritic structures or whiskers at the edges of coated substrates when air knives are used to control the coating weight in a slow'speed dip-coating process.

I have found that by mechanically wiping the edge of a slow speed galvanizing line at the proper location, the formation of whiskers is avoided.

One embodiment of my invention is shown in the attached figures in which:

FIG. 1 is a diagrammatic elevation view of a hot dip coating apparatus with parts broken away.

FIG. 2 is an isometric view of a coated steel strip passing between air knives and mechanical edge wipers.

As shown in FIG. 1, a strip enters a vessel 11 containing coating material 12 which in the galvanizing process is molten zinc, passes around a sinker roll 13 and moves upwardly between a pair of oppositelydisposed air knives 14 and is being contacted at its edges by wipers 16. The portion of the wiper in contact with the strip edge is A-shaped (FIG. 2). The cross bar 17 of the A actually contacts the strip while the legs 18 prevent the wiper from slipping off the strip edge. The wiper has an extended handle 20 which is adjustably positioned in tubular holder 21 and is retained therein by set screw 22. Afiixed to holder 21 is an arm 24 which is carried by a support rod or axle 25 having integral retaining discs 26 at its ends. The edge wiper is positioned by placing the support rod 25 in a pair of toothed racks 27, only one of which is shown. A counterweight 28 is hung on a notch 29 in the arm to maintain sufficient bearing pressure of the wiper against the jet. Thus the wiping is accomplished while the zinc is still in the molten state and not after it becomes solidified. If the wiper is closer than 25 inch from the air jet, the airis turbulent and interferes with the wiping action.

The position of the edge wiper may be adjusted vertically by use of set screw 22 and horizontally to accommodate various widths of strip by repositioning the support rod 25 in the toothed rack 27.

Edge wipers for removing excess coating material from strip edges are known. However, when an air knife is used, the vertical distance in which the wiper must operate is confined to about 4 inches, that being the distance between the bath and the air knife. Previous wipers, such as shown in LeCroy US. Pat. No. 3,536,038 do not have the necessary compactness to operate in this location.

It can readily be seen from the foregoing that I have invented means for preventing the formation of whiskers in slow speed hot dip coating lines in which the coating weight is controlled by use of an air knife.

I claim:

1. In an apparatus for applying a coating to a moving substrate which includes a vessel for containing liquid coating material, means mounted internal to said vessel and external to said vessel for conducting said substrate through said coating material, and a fluid nozzle mounted above said vessel and adapted to direct a fluid jet toward said substrate for controlling the weight and distribution of the coating, the combination therewith of an apparatus for removing excess coating material from the edges of said substrate, said apparatus comprising a wiper adapted to contact the edge of a moving substrate beneath the point of impact of said fluid jet from said fluid nozzle, and means for vertically and transversely adjusting and maintaining said wiper in beating relation against the edge of said substrate,

said last-named means comprising:

a rod element integral with said wiper, lying in the plane of said substrate extended, and extending vertically through a tubular holder member having locking means therewith whereby to vertically adjust said wiper;

a lever arm extending generally horizontally from said holder member in the direction away from the substrate and pivoted about a shaft extending through an intermediate section of said arm and a counter-weight adjustably supported on the free portion of said arm whereby to adjustably bias the wiper with respect to said substrate edge; and Y rail means including pairs of complementary notches therein adapted to support said shaft therebetween and whereby, through selection of appropriate notch ,supports, the total assemblage of shaft, lever arm and wiper may be adjusted in the direction normal to said edge. 

1. In an apparatus for applying a coating to a moving substrate which includes a vessel for containing liquid coating material, means mounted internal to said vessel and external to said vessel for conducting said substrate through said coating material, and a fluid nozzle mounted above said vessel and adapted to direct a fluid jet toward said substrate for controlling the weight and distribution of the coating, the combination therewith of an apparatus for removing excess coating material from the edges of said substrate, said apparatus comprising a wiper adapted to contact the edge of a moving substrate beneath the point of impact of said fluid jet from said fluid nozzle, and means for vertically and transversely adjusting and maintaining said wiper in bearing relation against the edge of said substrate, said last-named means comprising: a rod element integral with said wiper, lying in the plane of said substrate extended, and extending vertically through a tubular holder member having locking means therewith whereby to vertically adjust said wiper; a lever arm extending generally horizontally from said holder member in the direction away from the substrate and pivoted about a shaft extending through an intermediate section of said arm and a counter-weight adjustably supported on the free portion of said arm whereby to adjustably bias the wiper with respect to said substrate edge; and rail means including pairs of complementary notches therein adapted to support said shaft therebetween and whereby, through selection of appropriate notch supports, the total assemblage of shaft, lever arm and wiper may be adjusted in the direction normal to said edge. 